This relates to imaging systems and, more particularly, to imaging systems that produce rotated, compressed images.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
During operation, an electronic device having a digital image sensor may be held in a vertical or horizontal orientation when capturing images. It may therefore be desirable to provide electronic devices that produce JPEG images having vertical or horizontal orientations. Conventional JPEG images are coded into minimum coded units (MCUs). MCUs typically contain multiple blocks of image pixels. Conventional devices that provide JPEG images may produce JPEG images rotated into different orientations (e.g., vertical or horizontal) by decompressing the JPEG image, rotating the image, and re-compressing the image. Each JPEG compression results in loss of data and therefore loss of image quality. Some devices provide rotated JPEG images by rotating blocks of pixels and arranging MCUs in a rotated image such that each MCU in a rotated image contains different pixel blocks than the MCUs of a non-rotated image. Since MCUs are encoded differentially (i.e., encoded such that the encoding of one pixel block in an MCU depends on the prior encoding of another pixel block in the MCU), this change in the pixel blocks included in an MCU introduces a need for expensive processing and memory storage to account for the new differential encoding in the rotated image.
It would therefore be desirable to provide improved imaging systems that produce rotated JPEG images.